All electronic display technologies are composed of a large array of display picture elements, called pixels, arranged in a two-dimensional matrix. Color is added to these displays by subdividing each pixel element into three-color subpixels. The electronic display technologies can be further divided into a category known as flat-panel displays. The basic structure of a flat-panel display comprises two glass plates with a conductor pattern of electrodes on the inner surfaces of each plate with additional structure to separate the plates or create a channel. The conductors are configured in a x-y matrix with horizontal and vertical electrodes deposited at right angles from each other to allow for matrix addressing. Examples of flat-panel displays include plasma displays, plasma addressed liquid crystal (PALC) displays, field emission displays (FED), and the like.
Almost all flat-panel three-dimensional or multiple view displays are constructed by aligning a lens array or an array of slits to a preexisting display system.
U.S. Pat. Nos. 2,209,747, 4,717,949, 5,457,574, and 5,838,494 disclose stereoscopic display devices with an array of thin, vertical, parallel, equidistant, light emitting elements formed as lines behind a flat, transmissive, electronically controlled display panel, such as a cathode ray tube (CRT) or a liquid crystal display (LCD), generating the perception of three-dimensional images for an observer. The displays realize stereoscopic viewing without using any ancillary equipment, such as spectacles, that direct optical images of different polarized light components to the right and left eyes, respectively.
U.S. Pat. Nos. 2,209,747 and 4,717,949 disclose placing an opaque screen with a plurality of transparent slits in front of another screen, which displays a stereoscopic pair of images made up of alternating strips. Each strip displays a thin vertical section of one of the stereo pair of images. The strips are arranged so that the first strip displays a section of the right eye image, the second strip displays a section of the left eye image, the third strip displays a section of the right eye image and so on. The screen with the transparent slits is placed at a fixed distance in front of a picture so that an observer sees only the right eye strips through the slits with his right eye and only the left eye strips through the slits with his left eye. This technique of displaying stereographic pictures is known as the Hess system. For good image fidelity, the slits have to be very thin, relative to the opaque area that separates the slits, in order to block a large fraction of the light coming from the display. This makes it difficult to obtain bright images.
U.S. Pat. Nos. 5,457,574 and 5,838,494 disclose a three-dimensional display apparatus using a lenticular lens sheet. Referring to FIG. 1, observation positions R and L correspond to the view points of the right and left eyes. A lenticular lens sheet 40 contains an array of lenticular lenses where each lens has the same radius of curvature and a lens effect in one direction aligned to the electronic display 45 on which linear images are formed. On the electronic display 45, linear images which are obtained by dividing two images having parallax are formed based on the different, right and left view points, along the longitudinal direction of the respective lenticular lenses of the lenticular lens sheet 40. More specifically, alternating images 45a and 45b spaced on the lenticular lens spacing form the two parallax images viewed at points R and L.
Another method of generating a three-dimensional image without using glass is disclosed in U.S. Pat. No. 5,790,086. The patent is drawn to a device for creating a three-dimensional image by varying the distance of the image from the viewer pixel by individual pixel. The invention employs an array of extremely small, specially designed light-refracting optical elements which are formed such that the focal length of the elements varies across the surface of the optical element. By minutely displacing the entry point at which light is input to these optics for different pixels within an image, a complete image is presented to the viewer. The image contains certain elements which appear closer to the viewer while other elements appear farther from the viewer, mimicking the view of a real-world scene.
Prior art techniques for generating a three-dimensional image or multiple view image required a difficult alignment of either the lens array sheet or a sheet with an array of slits to the electronic display. Fabricating large lens arrays with tight tolerances have been difficult and fabricating large flat panel displays has been next to impossible.
Plasma display panels (PDP) are presently being constructed using the three electrode surface discharge structure, as disclosed in U.S. Pat. No. 4,833,463 and U.S. Pat. No. 5,661,500. FIG. 2 illustrates the basic structure of a surface discharge AC plasma display made using standard technology. The PDP can be broken down into two parts, a top plate 10 and a bottom plate 20. The top plate 10 has rows of paired electrodes referred to as the sustain electrodes 11a and 11b. The sustain electrodes are composed of wide transparent indium tin oxide (ITO) electrodes 12 and narrow Cr/Cu/Cr bus electrodes 13. The sustain electrodes 11 are covered with a thick (25 μm) dielectric layer 14 so that they are not exposed to the plasma. A magnesium oxide layer (MgO) 15 is deposited over the dielectric layer to enhance secondary emission of electrons and to improve display efficiency. The bottom plate 20 has columns of address electrodes 21 with barrier ribs 22 formed between them. Alternating red 23R, green 23G, and blue 23B phosphors are deposited into the channels between the barrier ribs 22 to provide color for the display. The top and bottom plates are frit sealed together and the panel is evacuated and backfilled with a gas mixture containing xenon gas.
The basic operation of the plasma display requires a plasma discharge whereby the ionized xenon generates ultraviolet (UV) radiation. This UV light is absorbed by the phosphor and converted into visible light. To address a pixel in the display, an AC voltage which is large enough to sustain a plasma but not large enough to ignite one is applied across the sustain electrodes 11. A plasma is analogous to a transistor in that, as the voltage is increased, nothing happens until a specific voltage is reached, at which point it turns on and current flows. Then an additional short voltage pulse is applied to the address electrode 21, which adds to the sustain voltage and ignites the plasma by adding to the total local electric field, thereby breaking down the gas into a plasma. Once the plasma is formed, electrons are pulled out of the plasma and deposited on the MgO layer 15. These electrons are used to ignite the plasma in the next phase of the AC sustain electrodes. To turn the pixel off, an opposite voltage must be applied to the address electrode 21 to drain the electrons from the MgO layer 15. At that point, there is no priming charge left to ignite the plasma in the next AC voltage cycle on the sustain electrodes. Using these priming electrons, each pixel can be systematically turned on or off. To achieve gray levels in a plasma display, each video frame is divided into 8 bits (256 levels) and, depending on the specific gray level, the pixels are turned on during these times.
U.S. Pat. No. 4,896,149 discloses and demonstrates the use of plasma channels to address a liquid crystal display. The PALC display, illustrated in FIG. 3, relies on the highly non-linear electrical behavior of a relatively low-pressure (10–100 Torr) gas, usually helium, confined in many parallel channels. A pair of parallel plasma address electrodes 36 are deposited in each of the plasma channels 35, and a very thin glass microsheet 33 forms the top of the channels. The plasma channels 35 are defined by barrier ribs 34. A liquid crystal layer 32 on top of the microsheet 33 is the optically active portion of the display. A cover sheet 30 with transparent conducting address electrodes 31 running perpendicular to the plasma channels 35 lies on top of the liquid crystal 32. Conventional polarizers, color filters, and backlights, such as those found in other liquid crystal displays, are also commonly used.